Printing plate locking device

ABSTRACT

Device for locking a printing plate onto a cylinder of a rotary press which enables the plate to be mounted and tensioned in register for operative rotation of the cylinder in either direction. A pair of grippers, each having a head for engagement with a respective opposite end portion of a plate wrapped around the cylinder, are mounted in a carrier transversely of the cylinder periphery and are each resiliently urged for independent plate-tensioning movement. Adjustment means is engageable alternatively with whichever gripper is to locate the operatively leading end portion of the plate to prevent said movement thereof so as to establish the register of the plate, while leaving the other gripper free to move for tensioning it.

United States Patent Primary Examiner-William B Penn Assistant Examiner-E. M. Coven AttorneyNorris & Bateman ABSTRACT: Device for locking a printing plate onto a cylinder of a rotary press which enables the plate to be mounted and tensioned in register for operative rotation of the cylinder in either direction. A pair of grippers, each having a head for engagement with a respective opposite end portion of a plate wrapped around the cylinder, are mounted in a carrier transversely of the cylinder periphery and are each resiliently urged for independent plate-tensioning movement. Adjustment means is engageable alternatively with whichever gripper is to locate the operatively leading end portion of the plate to prevent said movement thereof so as to establish the register of the plate, while leaving the other gripper free to move for tensioning it.

PATENTEU DEC 7 I971 SHEET 1 [IF 2 PATENTED DEC 7 |97| SHEET 2 OF 2 Fig. 2.

Invcnlor MICHAEL LEONARD HART 52 PRINTING PLATE LOCKING DEVICE This invention relates to printing plate locking devices for incorporation in printing cylinders of rotary printing presses, particularly but not exclusively web offset printing presses.

Web ofiset press printing plates are usually made of thin sheet metal secured around the periphery of the printing cylinder by a plate-locking device incorporated in a channel across said periphery and having grippers which engage preformed hooked leading and trailing edge portions of the plate. The leading edge of the plate is positively located with respect to the cylinder while the trailing edge is resiliently urged towards the leading edge gripper so as to tension the plate.

The object of the present invention is to provide a printing plate locking device for incorporation in a printing cylinder which permits operative rotation thereof in either direction as well as facilitating adjustment of the positioning of a plate on the cylinder and which is of compact construction and simple and reliable to operate.

In accordance with the present invention a printing plate locking device includes a carrier providing a channel having a mouth extending across the periphery and parallel to the axis of a printing cylinder in use, and a pair of grippers mounted in the cannel with parallel head portions adjacent the channel mouth and respectively adapted to engage opposite end portions of a printing plate wrapped around the cylinder periphery in use, characterized in that each gripper (15, 16; 215, 216) is resiliently urged by spring means (25; 225) for independent movement relative to the other gripper and the channel in a direction serving to tension the plate in use, and by adjustment means (26; 226) engageable alternatively with either gripper to prevent said movement only of the gripper so engaged.

Two preferred embodiments of the invention are now described with reference to the accompanying drawings wherein:

FIG. I shows a perspective view of a first embodiment of the invention partially broken away for clarity;

FIG. 2 is a cross-sectional view along the line 2-2 of FIG. 1; and

FIG. 3 shows a perspective view of a second embodiment of the invention.

Referring to FIGS. 1 and 2 a first embodiment of a printing plate locking device is shown mounted in a printing cylinder of a conventional web offset press. Cylinder 10 rotates on stub axles l1 operatively joumaled in the press and may be rotated in either direction depending on the operation being carried out by the press.

A rectangular section groove 12 extends across the periphery of the cylinder parallel to its axis, in which is received a carrier block 13 providing a channel formation longitudinally of block 13 with a mouth defined by convergent lip portions 14 of the channel walls into which mouth can extend hooked leading and trailing edge portions of a printing plate operatively wrapped around the cylinder periphery.

A pair of plate grippers l5, 16 are located in the channel and include respective head portions 17, 18 with respective jaws 19, 20 directed towards each other but spaced apart in the mouth of the channel to engage said plate edge portions; and respective body portions 21, 22 located adjacent and parallel to respective sidewalls of the channel. A pair of parallel fulcrum shafts 23, 24 are journaled in the end walls of block 13 so that they extend along the bottom of the channel and pass through bores in extensions of the respective gripper body portions 21, 22 to pivot them independently for angular movement, the shafts being freely rotatable in said bores.

Spring-loaded plungers 25 are located in bores at intervals along each sidewall of the carrier block 13 so that they bear on the gripper bodies 21, 22 and resiliently urge the gripper heads 17, 18 towards each other.

Adjustment means in the form of a set of adjusting bolts 26 (one only of which is shown in the drawing) are engaged in threaded bores in one of the sidewalls of the carrier block 13 with their shanks 27 passing freely through apertures in the body 22 of the gripper 16 adjacent that sidewall. Heads 28 of the bolts provide abutment formation which are located in the center of the channel between the gripper bodies where they can be rotated by means of a spanner inserted through the mouth of the channel. By screwing the bolts 26 further into the carrier block wall a domed annular face 29 of each bolt where the head 28 adjoins the shank 27 is brought into engagement with the side of gripper body 22v remote from its respective set of spring plungers 25 so as to move the gripper 16 against the springs until it abuts the adjacent sidewall of the carrier block to locate it rigidly. Alternatively by screwing bolts 26 further out of the carrier block wall said faces 29 are moved clear of the gripper 16 but second domed faces 30 defining the outermost end of each bolthead 28 engage abutment faces 31 on the other gripper body 21 moving it against its springs until it abuts the adjacent sidewall of the carrier block.

Abutment screws 32 (of which only one is shown in the drawing) are located at intervals in threaded bores in each gripper body 21, 22 with their heads 33 protruding into the space between the grippers for engagement by a spanner as before, and the end faces of their threaded shanks 34 projecting through the face of the gripper body adjacent the sidewall of the carrier block, adjustment of these screws permitting variations in the angular position at which each gripper abuts the block under the action of the bolts 26.

Fulcrum shaft 24 includes one or more cams 35 each in engagement with a cam follower 36 in the form of a roller 37 pivoted in a formation 38 of the body 21 of gripper 15 which protrudes towards the other gripper 16. A like cam or cams 39 on shaft 23 each engage similar cam followers 40 in the form of rollers 41 pivoted in formation 42 of body 22 of gripper 16. Assuming that the respective gripper is not rigidly locked by the adjusting bolts 26 it can be angularly moved by rotating the appropriate shaft 23 or 24. The respective cams and cam followers are staggered on each side of the channel to provide working clearance, and a pair of sleeves 43 and 44 pivotally mounted in an end wall of the cylinder 10 engage the respective shafts 23 and 24 and are rotatable by means of projecting squared ends 45 and 46 with which a key can be engaged.

Assuming that the cylinder 10 is to rotate operatively in the direction indicated by arrow 47, the leading hooked end portion of a printing plate operatively mounted thereon will be engaged in the jaws 20 of gripper 16 while the like trailing portion will be engaged in jaws 19 of gripper 15. For this mode of operation adjusting bolts 26 are screwed into the carrier wall until gripper body 22 is positively located in rigid abutment against said wall. The exact circumferential register of the plate relative to the cylinder is adjusted by means of the set of abutment screws 32 in that gripper body 22. This leaves the other gripper 15 free to move angularly on its fulcrum shaft 23 so that the plate is tensioned by the set of plungers 25 acting on that gripper. If it is desired to release the plate from the cylinder shaft 24 is rotated to bring cams 35 into engagement with the followers 38 of the gripper 15 to release the tension so that the plate can be unhooked.

If it is desired that the cylinder 10 shall be operatively rotated in the direction opposite to that indicated by arrow 47 so that the leading end of the plate becomes that engaged by gripper 15 instead of gripper 16, adjusting bolts 26 are screwed further out of the sidewall of carrier block 13 freeing gripper 16 for tensioning the trailing end of the plate and rigidly locating gripper 15 in manner corresponding to that described above. In this case the movable tensioning gripper 16 can be released to free the plate by rotating shaft 23.

The whole plate-locking device can be removed from the cylinder 10 as a unit by disengaging carrier block 13 from the groove 12.

FIG. 3 illustrates a second embodiment of the invention, parts having the same construction and function as in the first embodiment being given the same reference numerals prefixed by a numeral 2. The operation of locating one of the grippers 215 or 216 positively by means of adjusting bolts 226 to receive the leading edge of the printing plate, leaving the other gripper resiliently urged angularly about a respective fulcrum shaft 223 or 224 by its set of spring plungers 225 is exactly the same as was described for the first embodiment. Again abutment screws 232 are provided to adjust the register of the fixed gripper.

instead of the cam and cam follower gripper release mechanism of the first embodiment, fulcrum shaft 224 serves purely to locate gripper 216 and is mounted in brackets 250 (one only shown) attached to the base wall of the carrier block 213. The other fulcrum shaft 223 pivotally locates gripper 215 but is freely rotatable in bearings (not shown) formed in the carrier, one end of the shaft extending through the end wall of the cylinder and terminating in a squared end section 245 enabling it to be rotated by a key. A worm 251 on shaft 223 engages a worm wheel 252 journaled at 253 in the base wall of carrier block 213, and having an axial threaded bore 254. In this bore is engaged screw stem 255 of jack 256. Head 257 of the jack is aligned with lugs 258 on each of the gripper bodies 221 and 222, said lugs projecting towards each other across the center region of the channel between the grippers. Rotation of shaft end 245 enables the head 257 of jack 256 to be moved away from the base of the carrier block so that it moves either or both grippers 215, 216 angularly on their respective fulcrum shafts 223, 224 against the pressure of the spring plungers 225 to enable a plate to be released from engagement therewith as described in connection with the first embodiment.

Various modifications in the constructions above described are envisaged. For example the adjustment bolts 26 may be replaced by a camshaft within the channel, abutment formations in the form of cams having alternative engagement with the two grippers to lock one or other of them against angular movement. The cam and follower or worm and jack gripper release mechanism may be omitted in other embodiments, leaving the plate to be released by forcing the grippers apart by a handtool or other means.

The number of adjustment bolts 26 or 226, abutment screws 32 or 232 and cams 35 with cam followers 26, 40; or jacks 256 required will depend on the overall length of the particular plate-locking assembly. Two or more assemblies may be located end to end across a single cylinder for reversible processing of multiple width webs, and in the case of the second embodiment single shafts 223 and 224 may extend through or be coupled end to end in, for example, two assemblies; the grippers of respective ones of the assemblies being released by rotation of a respective shaft.

it is also anticipated that the invention may be applied to plate-locking devices of the kind described in our copending US. Pat. application No. 739,380, in which the plate grippers are in sections and can be moved longitudinally relative to the carrier to accommodate a range of plate widths.

instead of the operative parts of the locking device being located in a channel in a carrier block as described above they may be located in a channel formed in the cylinder itself so that the channel walls are integral therewith.

lclaim:

1. A printing plate locking device for a printing cylinder including a carrier adapted to be mounted on said printing cylinder providing a channel having a mouth extending across the periphery and parallel to the axis of said printing cylinder, and a pair of grippers mounted in the channel with head portions parallel to one another and adjacent the channel mouth and respectively adapted to engage opposite end portions of a printing plate wrapped around the cylinder periphery, each gripper being resiliently urged by spring means for independent movement relative to the other gripper to tension the plate, characterized by adjustment means providing a movable abutment member disposed within the channel and mounted for movement transversely of the channel into alternate engagement with one or the other of the grippers to prevent said movement only of the gripper so engaged, said abutment member comprising a rotatable axially displaceable bolt having screw thread mounting in said carrier and a head located between said pair of grippers whereby rotation of the bolt in one direction may engage a first side face at said head with one of said grippers to force one gripper into fixed relation with one side of the channel for there receiving the leading edge of a printing plate during rotation of the printing cylinder in a first direction and rotation of the bolt in the opposite direction may engage a second side face at said head with said other gripper to force the other gripper into fixed relation with the other side of the channel for there receiving the leading edge of a printing plate during rotation of the printing cylinder in a second direction.

2. A locking device according to claim 1 characterized in that the spring means comprises a plurality of compression spring-loaded plungers located in bores in sidewalls of the carrier.

3. A locking device according to claim 1 characterized in that each gripper is pivotally mounted in the channel on a respective rotatably mounted fulcrum shaft for the independent movement.

4. A locking device according to claim 3 characterized in that each fulcrum shaft includes a cam engaged with a respective follower portion of the gripper mounted on the other shaft so that said gripper is angularly movable against the spring means to release the tension on the plate.

5. A locking device according to claim 1 wherein said carrier channel has opposed sidewalls and each said gripper is disposed adjacent an opposite sidewall and characterized by means for adjusting the position of each gripper relative to the adjacent sidewall when engaged by the adjustment means.

6. A locking device according to claim 5 characterized in that the gripper position adjusting means is a bolt having a threaded shank in engagement with a threaded bore in the respective gripper (15, 16; 215, 216) and projecting to abut a carrier sidewall and a head between the pair of grippers whereby the bolt can be rotated to vary the position of said gripper relative to an adjacent sidewall of the carrier when engaged by the adjustment means.

7. A locking device according to claim 1 characterized in that the carrier is a block located in a mounting groove in the cylinder periphery.

8. A printing plate locking device as defined in claim 1 wherein said bolt passes freely through one of said grippers to dispose said opposed head faces transversely between said grippers. 

1. A printing plate locking device for a printing cylinder including a carrier adapted to be mounted on said printing cylinder providing a channel having a mouth extending across the periphery and parallel to the axis of said printing cylinder, and a pair of grippers mounted in the channel with head portions parallel to one another and adjacent the channel mouth and respectively adapted to engage opposite end portions of a printing plate wrapped around the cylinder periphery, each gripper being resiliently urged by spring means for independent movement relative to the other gripper to tension the plate, characterized by adjustment means providing a movable abutment member disposed within the channel and mounted for movement transversely of the channel into alternate engagement with one or the other of the grippers to prevent said movement only of the gripper so engaged, said abutment member comprising a rotatable axially displaceable bolt having screw thread mounting in said carrier and a head located between said pair of grippers whereby rotation of the bolt in one direction may engage a first side face at said head with one of said grippers to force one gripper into fixed relation with one side of the channel for there receiving the leading edge of a printing plate during rotation of the printing cylinder in a first direction and rotation of the bolt in the opposite direction may engage a second side face at said head with said other gripper to force the other gripper into fixed relation with the other side of the channel for there receiving the leading edge of a printing plate during rotation of the printing cylinder in a second direction.
 2. A locking device according to claim 1 characterized in that the spring means comprises a plurality of compression spring-loaded plungers located in bores in sidewalls of the carrier.
 3. A locking device according to claim 1 characterized in that each gripper is pivotally mounted in the channel on a respective rotatably mounted fulcrum shaft for the independent movement.
 4. A locking device according to claim 3 characterized in that each fulcrum shaft includes a cam engaged with a respective follower portion of the gripper mounted on the other shaft so that said gripper is angularly movable against the spring means to release the tension on the plate.
 5. A locking device according to claim 1 wherein said carrier channel has opposed sidewalls and each said gripper is disposed adjacent an opposite sidewall and characterized by means for adjusting the position of each gripper relative to the adjacent sidewall when engaged by the adjustment means.
 6. A locking device according to claim 5 characterized in that the gripper position adjusting means is a bolt having a threaded shank in engagement with a threaded bore in the respective gripper (15, 16; 215, 216) and projecting to abut a carrier sidewall and a head between the pair of grippers whereby the bolt can be rotated to vary the position of said gripper relative to an adjacent sidewall of the carrier when engaged by the adjustment means.
 7. A locking device according to claim 1 characterized in that the carrier is a block located in a mounting groove in the cylinder periphery.
 8. A printing plate locking device as defined in claim 1 wherein said bolt passes freely through one of said grippers to dispose said opposed head faces transversely between said grippers. 